For some horology enthusiasts, it’s not enough for a watch to look stunning in broad daylight – it has to look exceptional in the dark too. Typically used in dive or other tool watches designed for maximum legibility even in low lighting conditions, the glow-in-the-dark substance known as lume often goes beyond mere function to give timepieces a unique character. Usually applied to the hour and minute markers as well as hands, lume highlights various forms of typography and hand shapes. You’ll also see it used on other interesting dial details such as the stars and moon on lunar displays, or representations of globes on world timers. It has come a long way not just in form but substance as well. The earliest lume took the form of radioactive, radium-based paints, which killed or made ill many women in the 1920s who were employed to apply them to watch dials. Today, most watch brands use some form of Super-Luminova, a non-hazardous, strontium aluminate-based substance rooted in Luminova pigments invented by Japanese company Nemoto & Co in 1993. Here are the latest ways in which watch brands are taking lume to the next level.

(Related: The new Bell & Ross BR 03-92 Diver Full Lum might be the brightest watch underwater)

(Related: Three new timepieces to take note of )

(Related: Jaquet Droz’s established Grande Seconde Quantieme gets new variations)